Window.ClosingHandler cannt catch closeEvent after refresh

i use Window.ClosingHandler to capture refresh and close Event for Browser,but after i refresh the page, and then close the browser,the following code didnt work,cannot capture the ClosingEvent.
Window.addWindowClosingHandler(new Window.ClosingHandler() {
@Override
public void onWindowClosing(ClosingEvent closingEvent) {
/* my code */
}
});